While you quench your thirst from the summer heat, think about your drink.

Everyone knows that sugary soda pop is full of calories — and bad for your teeth to boot. But a Purdue University study suggests that artificial sweeteners might also make weight control more difficult. The findings appeared in the February 2008 issue of Behavioral Neuroscience, a journal published by the American Psychological Association.

In a five-week experiment using 17 rats, those given yogurt sweetened with zero-calorie saccharin consumed more total calories and didn't make up for it by cutting back later. They ended up gaining more weight and body fat than those with the sugar-sweetened yogurt.

The psychologists who performed the study theorize that when the body tastes sweetness, it prepares itself for a calorie load. If sweetness comes without calories — as with artificial sweeteners — people keep eating or else the body reduces its calorie-burning metabolic activity.

Karen Collins, dietitian for the American Institute for Cancer Research, points out that a small study involving rats shouldn't be used as a definite conclusion for humans.

The studies strike home because I enjoy an ice-cold soft drink as a midmorning pick-me-up. But I usually end up feeling ravenous within the hour. Is it psychological? Does the carbonation expand my stomach so it feels empty? I don't know.

But for me, the study would have more credence if instead of saccharin the researchers had used aspartame (NutraSweet) or sucralose (Splenda). These are more commonly used to sweeten today's diet drinks, sugar-free puddings and yogurts, etc.

Coca-Cola's TAB, one of the first diet drinks that came on the market in the 1960s, uses a combination of saccharin and aspartame, but it has a tiny share of the market compared with Diet Coke and Diet Pepsi.

In an AICR press release, Collins names other studies showing that diet sweeteners help maintain weight loss. In one, 163 obese women were put on a 19-week weight-loss program. Some were asked to consume, and some to avoid, artificially sweetened food and drinks during the program, as well as a one-year maintenance and a two-year follow-up period. Both groups averaged a loss of 10 percent of their body weight. But during the follow-up period, the artificial sweetener group showed better weight maintenance.

The study also showed a positive correlation with exercise and self-reported eating control; exercise is good whether or not you use artificial sweeteners.

Observational studies have concluded that the use of artificial sweeteners is more common in overweight than normal-weight people. But this doesn't necessarily mean that sweeteners make people overweight. Were these people already overweight and thus chose artificial sweeteners to help, or did they gain weight only AFTER they began using the sweeteners? Or did they allow themselves an extra brownie as long as it's washed down with a Diet Coke?

Collins' advice from these findings is to use artificial sweeteners only as a substitute for — not in addition to — high-calorie foods. And a good alternative to either diet or sugar-sweetened sodas is plain old-fashioned water.

E-mail: [email protected]